Philosophy 100 Essential Thinkers

by Philip Stokes

Thales was the first thinker to try to account for the nature of the world without appealing to the wills and whims of anthropomorphic, Homerian gods.

Thales claimed that god is in all things. According to Aetius, Thales said the mind of the world is god, that god is intermingled in all things, a view that would shortly appear contemporaneously in a number of world religions, most notably Buddhism in India.

According to Pythagoras, the ultimate nature of reality is number.

This idea developed out of his theory of music, in which he proved that the intervals between musical tones could be expressed as ratios between the first four integers (the numbers one to four). Since part of Pythagoras’ religious teaching consisted in the claim that music has a special power over the soul, infused as it is into the very fabric of the universe, the belief that number is the ultimate nature of reality quickly followed.

Both the triangle and the number 10 – the decad – became objects of worship for the Pythagoreans. In Pythagorean thought, the number 10 is the perfect number because it is made up of the sum of the first four integers, as shown in the tetractys. The integers themselves were thought to represent fundamental ideas – the number one representing the point, two the line, three the surface and four the solid. Further, it was thought that there were ten heavenly bodies – five planets, the sun, the moon, the earth and a mysterious and invisible ‘counter-earth’ (probably invented to make the celestial number up to ten) all revolving around a central fire.

After Pythagoras’ death, his school splintered into two camps. One maintained his religious and mystical teachings, while the other concentrated on his mathematical and scientific insights. The latter continued to believe the nature of the universe must be essentially arithmetical.

Units of number, points, were somehow thought to possess spatial dimensions and be the ultima...

Following Thales, he criticized the Homerian concept of anthropomorphic gods.

cultural relativism,

Xenophanes remarked that Homer’s gods were simply a reflection of Homerian culture.

Likewise, he criticized Pythagoras’ doctrine of the transmigration of souls, making fun of the idea that a human soul could inhabit another animal. Xenophanes held some vague concept of a single deity that was ‘in no way like men in shape or in thought’ but rather ‘causing all things by the thought of his mind’.

Like Thales before him, Xenophanes speculated about the underlying principles of natural phenomena.

the world periodically dried up, returning to its original muddy state, trapping and preserving the earth’s creatures as it did so before reversal of the process.

Philosophical certainties could not be had, according to Xenophanes, for even if we chance to hit upon the truth, there is no way of knowing for certain that things are as we think they are.

Everything is in a state of flux, or change, and war and strife between opposites is the eternal condition of the universe.

‘All things are an exchange for Fire, and Fire for all things…the transformations of Fire are, first of all, sea; and half of the sea is earth, half whirlwind’.

Mirroring the Oriental concepts of yin and yang, Heraclitus believed the

dynamism between opposites was the driving force and eternal condition of the universe.

‘Men do not understand that being at variance it also agrees with itself, there is a harmony, as with the bow and the lyre’. Heraclitus continues to tell us that ‘God is day and night, winter and summer, war and peace, fullness and hunger’. Strife and opposition are both necessary and good, for the concept of universal tension ensures that whilst opposites...

the other: ‘The sun may not overstep his measure; for the Erinyes, the handmaids of Jus...

This universal tension ensures that change is continual, that everything is in a state of flux. Permanence does not exist in the universe, only the permanent condition of change as a result of the transformations of Fire. This implies that whilst nothing remains changeless within the universe, the universe itself i...

His works are written in aphoristic and prophetic style, with a clear contempt for those that cannot see what is clearly before them.

Heraclitus is undoubtedly a mystic and there are strong affinities between his writings and the Chinese classic Tao Te Ching supposedly written by Lao Tzu (‘Old Master’) at around the same time. Whether Heraclitus had any contact with the oriental tradition, or vice versa, is impossible to determine.

Heraclitus’ conception of reality as a process, an ever-changing flux, stands in stark contrast to almost the entire subsequent development o...

Little is known of Parmenides’ life and background, and fragments of a poem entitled On Nature are all that survive of his work.

Nevertheless, it contains one of the first examples of reasoned argument in which, perhaps as a reaction to Heraclitus, Parmenides attempts to prove that change is impossible and that reality is singular, undivided and homogenous.

Parmenides distinguishes between an inquiry into what is and an inquiry into what is not. The

latter, he says, is impossible.

The argument turns principally on two complex issues. First, exactly what is meant by ‘exists’ here?

What is the difference between existing in the world and existing in the mind?

Second, what are the connections between thoughts, words, and things?

If that debate started with Parmenides, it has taxed almost every major thinker ever since, up to and including the seminal works of the twentieth century by philosophers such as Bertrand Russell, Ludwig Wittgenstein and W.V. Quine.

Since Parmenides proposed that to think of something is to give it some semblance of existence, then one cannot think of anything that is truly ‘not’. It follows that one can only think of that which is. Now comes the second part of Parmenides’ deductive reasoning, the first known example of a formal deduction in the history of Western thought. For to think of anything that is implies the existence of something that is not. If something is green, it is not red, if something is a man, it is not a dog, a house is not a cart, and so on. But since by his previous argument Parmenides has shown that negative existential claims are impossible, it seems one cannot make positive existential discriminations either. To distinguish X from Y, is to say that X is not Y, precisely that which Parmenides claims is impossible. Therefore, one cannot logically disc...

Therefore, Parmenides concludes, coming into being and passing away are illusory, change is illusory: everything is one, undivided, changeless and eternal.

Achilles can never catch the tortoise no matter how fast he runs

Zeno’s paradoxes are the first recorded example of argument by the logical technique of ‘reductio ad absurdum’ (literally, reduction to absurdity) in which an opponent’s view is shown to be false because it leads to contradiction.

Defending Parmenides’ view that the commonsense notions of change and plurality are illusory, Zeno developed a series of paradoxes to show that they lead to very uncommon, nonsensical conclusions, thereby proving that they cannot represent the true nature of the world.

Suppose Achilles decides to see how fast he can run the track in a stadium. Before he can reach the end he must first get to the half way point, but before he does so he must get to the halfway point of that, and the half way point of that, and so on indefinitely. If space is made up of an infinite series of points one can never move any distance at all; to complete a journey one would have to pass every point, and one cannot pass an infinite series of points in a finite amount of time. Similarly, in the famous Achilles and the Tortoise paradox, Zeno asks us to imagine Achilles giving the tortoise a head start. But before he can get to where the tortoise is, it will have moved a little farther on, and before he can get to that spot the it will have moved a little farther on again, and so on indefinitely. Achilles can never catch the tortoise no matter how fast he runs, for every time he moves the tortoise moves too. Therefore motion through time (i.e. change) is impossible.

In this way, Zeno tried to defend Parmenides’ view that the true nature of reality is an unchanging, indivisible whole.

Only by using modern set-theoretic mathematics, which abandons the Euclidean definition of a line as a series of points, has a reasonably satisfactory answer to Zeno been found.

‘The only thing I know is that I know nothing’

an itinerant philosopher

who taught solely by means of public discussion and oratory and never wrote any philosophical works of his own.

Unlike the Greek philosophers before him, Socrates was less concerned with abstract metaphysical ponderings than with practical questions of how we ought to live, and what the good life for man might be. Consequently he is often haile...

It is precisely his concern with ethical matters that often led him into conflict with the city elders, who accused him of corrupting the minds of the sons of the we...

ignorance.

‘beauty’,

‘the good’,

‘pi...

The greatest danger to both society and the individual, we learn from Socrates, is the suspension of critical thought.